Myo-inositol ester

Atkin RK, Barton GE, Robinson DK (1973) Effect of root-growing temperature on substances in xylem exudate of Zea mays. J Exp Bot 24 475-487 Atsmon D, Lang A, Light EN (1968) Contents and recovery of gibberellins in monoecious and gynoecious cucumber plants. Plant Physiol 43 806-810 Backus GE, Schrank AR (1952) Electrical and curvature responses of the Avena coleoptile to unilateral illumination. Plant Physiol 27 251-262 Bandurski RS (1978) Chemistry and physiology of myo-inositol esters of indole-3-acetic acid. In Wells W, Eisenberg F (eds) Cyclitols and phosphoinositides. Academic Press, London New York, pp 35-54... 

Nowacki J, Bandurski RS (1980) Myo-inositol esters of indole-3-acetic acid as seed auxin precursors of Zea mays L. Plant Physiol 65 422-427 Ohwaki Y, Tsurumi S, Nagao M (1974) Auxin transport in Vicia roots. In Plant growth substances 1973. Hirokawa, Tokyo, pp 1071-1078 Osborne DJ (1968) A theoretical model for polar auxin transport. In Vardar Y (ed) The transport of plant hormones. North-Holland, Amsterdam, pp 97-107 Osborne DJ (1974) Hormones and the shedding of leaves and bolls. Cotton Grow Rev 51 256-365... 

The simplest of the glycerophospholipids is phosphatidic acid, in which phosphate is linked to the third hydroxyl function, forming a phosphate ester. More complex glycerophospholipids are derivatives of phosphatidic acid in which one of several groups is attached commonly choline, ethanolamine, serine, or myo-inositol. Structures are collected in table 19.1. 

Amongst the cyclic polyols, inositols are most widely distributed in the plant kingdom.234 Out of nine stereoisomers, myo-inositol has the most widespread metabolic significance.235 The derivatives of myoinositol are also widespread. In plants, myo-inositol plays an important role in the biosynthesis of hemicelluloses and oligosaccharides it also occurs as a storage product (phytic acid), a coenzyme for sugar-transport, a precursor of phosphoinositides, and esters of in-doleacetic acid.47,113,238... 

Ms. Pat Hall and Drs. J. Nowacki and E. Epstein have provided our knowledge of the amounts and rate of metabolic turnover of the indolylic components of the kernels of lea mays (cf. 27, 28 Nowacki, unpublished Epstein, unpublished). This knowledge Fas enabled us, 1) to identify the "seed auxin precursor"—that is the compound which is transported from the seed to the growing shoot (39J, and 2) has provided a portion of the proof that IAA-myo-inositol and IAA are in reversible equilibrium in the shoot tissue. Proving that IAA and IAA esters are in reversible equilibrium in the tissue is essential if we wish to postulate hormonal homeostasis. 

Table II. They showed that tryptophan, IAA and IAA-myo-inositol are turning over—that is made and then destroyed, or used, at rates such that tJj was 5, 3.2 and 12 hrs, respectively. Such data permitted several important conclusions concerning the metabolism of these compounds, for example, that it is the IAA esters, and not tryptophan, which serve as a source of IAA for the germinating seed and secondly that the IAA-inositols are turning over at such a rapid rate that they must be in equilibrium with the IAA-myo-inositol glycoside pool perhaps acting as glycosylation reagents (Epstein, unpublished).

Dr. Hamilton earlier observed that ether extraction of tissue induced autolysis, liberating active esterases and glycosi-dases, and thus leading to more free IAA than extraction of tissue by polar, and thus, enzyme-denaturing solvents (35). Thus, we knew then that there were enzymes in the tissue capaBTe of hydrolyzing IAA esters. Much later, Kopcewicz demonstrated the presence of an enzyme system which could synthesize lAA-myo-inositol from IAA, ATP, Mg++ and CoASH (43). More recently, Mr. Lech Michalczuk (unpublished) has shown that IAA-CoA will acylate inositol only in the presence of other nucleotides. Thus, the reaction is complex, but there is no doubt that enzymes to make and hydrolyze the IAA esters are present in corn. 

The final step in the synthesis—replacement of the amino group in XI by a hydroxyl group—was carried out by Posternak28 by treatment with nitrous acid. Inversion occurred, giving a 10-15% yield of myo-inositol the other products of the reaction could not be identified. A much better yield (71 %) was achieved by the nitrous acid deamination of the penta-acetate ester of XI, rather than by deamination of the free inosamine.30,31 This method has been utilized30,31 for the preparation of myo-inositol- -C14 from nitromethane-C 14. 

In addition to the methyl ethers of dextro-, levo-, and myo-inositol which have been discussed in the preceding paragraphs, methyl ethers of most of the other inositols are now known. These compounds have been incidentally obtained in the course of other investigations—by the reduction of inososes formed from known ethers, by the inversion of tosyl esters of known ethers, and by opening the epoxide rings of anhydroinositols with methoxide ion. The individual compounds are listed in Tables II-X, pp. 192-203. 

While these results support a phosphate ester bridge between the glycerol and inositol, it does not prove where the bond is located on the inositol molecule. Inasmuch as the inositol phosphate isolated by alkaline cleavage from the parent phosphatidylinositol or the glycerophosphoinositol was optically active, the phosphate must be attached at the 1 or 4 position. Substitution at the 2 position of inositol would not yield an optically active product. Subsequently as will be discussed, observations from several laboratories have shown that the phosphate bond is between the sn- 3 position of the glycerol and the C-l hydroxyl on myo-inositol. 

Non-tryptamines.—The structure (1) of a new bromo-indole derivative, isolated from an Australian sponge of the genus Iotrocha, has been elucidated and confirmed by synthesis.4 The indole-3-acetic ester of myo-inositol occurs in rice kernels (Oryza sativa) 5a this is the first reported occurrence of this ester in a plant other than maize (Zea mays). 

Finally, a stereo chemically controlled reduction to give the axial alcohol (this would be the stereoselectivity expected with NaBH4 for example see Chapter 18) gives myo-inositol. The number and position of the phosphate esters can be controlled biochemically. This control is vital in the biological activity and would be difficult in the laboratory. 

Phytase phosphatase Aspergillus niger var. (1) myo-inositol- hexakisphosphate-3- phosphohydrolase (2) orthophosphoric-mono ester phosphohydrolase 3.1.3.8 3.1.3.2... 

Benzyl 2,2,2-trichloroacetimidate (bp 106-114 °C/0.07 kPa) alkylates alcohols in the presence of trifluoromethanesulfomc acid.311 Esters, imides, isopropylidene and benzylidene acetals are unaffected. This method allows the formation of benzyl ethers in molecules that are base-sensitive. In the example [Scheme 4,167],312 benzylation of the P-hydroxy ester 167.1.1 under the usual basic conditions would lead to retro-aldol reactions and/or elimination. A synthesis of the cellular messenger L-a-phosphatidyl-D-myo-inositol 3,4-bisphosphate exemplifies the use of trityl cation-promoted benzylation of two adjacent hydroxyls [Scheme 4.168].313314... 

Brearley, C.A., and Hanke, D.E., 1996a, Metabolic evidence for the order of addition of individual phosphate esters to the myo-inositol moiety of inositol hexakisphosphate in the duckweed Spirodelapolyrhiza L. Biochem. J. 314 227-233... 

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